Optical fiber communications systems support much of the total transmission capacity. Optical fiber communications provide a cost effective approach to transmitting numerous signals that may require large data rates and low latency times. However, an optical fiber communication system typically incorporates many individual optical fiber members, each optical fiber member requiring periodic testing to validate the integrity of each optical fiber member.
FIG. 1 shows an apparatus 100 for measuring an optical parameter for one of the fiber members in accordance with prior art. Processing unit 105 processes optical signal inputs 107, 109, and, 111 by instructing an optical N:1 switch 101 (e.g., an N:1 opto-mechanical switch) through an input selection port 113. The output of optical N:1 switch 101 approximately equals the selected signal input that is associated with one of the optical fiber members. Common measurement circuit 103 measures the output of optical N:1 switch 101 to determine a measured value of an optical parameter. Common measurement circuit 103 may measure one of a number of optical parameters, including an optical spectrum tilt (typically measured by an optical spectrum analyzer (OSA)), insertion loss, and a reflection coefficient (often measured by a reflectometer). Typically, it is not economically justifiable to dedicate a measurement circuit for each optical fiber member, and thus common measurement circuit 103 is shared among the optical fiber members.
Processing unit 105 obtains a measurement from common measurement circuit 103 and processes the measurement to provide a processing output 115. Processing unit 105 may further process the measurements with other obtained measurements to determine a measurement statistic (e.g., a measurement average and a measurement variability). Processing 105 typically repeats the measurement process for each optical fiber member.
Apparatus 100 may experience a hardware fault in which optical N:1 switch 101 gets “stuck” in one of the switching positions. With an opto-mechanical switch, the probability of a failure is typically correlated to the number of times that the opto-mechanical switch has switched. With such a failure mode, the output of optical N:1 switch 101 corresponds only to one of the signal inputs 107, 109, and 111 regardless of input selection 113. Processing circuit 105 may erroneously perceive that all optical fiber members are functioning properly based on the signal input that optical N:1 switch 101 is stuck at. Processing circuit 105 is typically not cognizant whether optical N:1 switch 101 is improperly functioning.
Thus, there is a need to provide apparatuses and methods for switching optical signals so that the functionality of a plurality of optical fiber members can be analyzed in a reliable manner.